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 Entered dateSiteRegionReactor typeEvent description
ENS 540984 June 2019 04:10:00LimerickNRC Region 1At 0145 EDT, on 6/4/19, Unit 2 was manually scrammed during a Rapid Plant Shutdown. At 64 percent reactor power, a Rapid Plant Shutdown was initiated due to lowering Main Condenser vacuum as a result of the loss of a plant electrical panel that powers Offgas System controls. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the Main Turbine Bypass Valves to the Main Condenser and normal level control using Feedwater and Condensate. Main Condenser Vacuum has been restored. The licensee notified the NRC Resident Inspector. Additionally, State and local government agencies were notified. Prior to restarting Unit 2, an evaluation needs to be done due to the Unit 1 Diesel currently out of service for maintenance. The Unit 1 Diesel is a power supply for some of the common systems under the Unit 2 Technical Specifications and therefore required.
ENS 5408324 May 2019 09:51:00LimerickNRC Region 1This 60-Day telephone notification is being made per the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of Limerick Generating Station Unit 2 containment isolation logic. On April 18, 2019, while performing a relay replacement on the Division 2/4 Main Steam Line logic, a partial containment isolation occurred due to a blown fuse. The following systems had components that actuated due to the partial isolation: Reactor Water Clean-Up System Primary Containment Instrument Gas System Drywell Chilled Water System Reactor Enclosure Cooling Water System Core Spray System The Residual Heat Removal System received an isolation signal; however, the system remained in service because the isolation was defeated in accordance with plant procedures. This event resulted in partial Group 2A, 3, 7A, 8A, and 8B isolations. The systems successfully functioned per the plant design and plant configuration. The licensee notified the NRC Resident Inspector.
ENS 5401521 April 2019 12:43:00LimerickNRC Region 1Event of Public Interest performed to notify State and Local agencies for emergency vehicle response required due to an on-site non-work related illness. The individual was unresponsive and was unable to be resuscitated due to the medical issue. The individual was outside the Radiological Controlled Area (RCA) and no radioactive material or contamination was involved. The NRC Resident Inspector was notified.
ENS 5401421 April 2019 08:46:00LimerickNRC Region 1This 60-Day telephone notification is being made per the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) to describe an invalid actuation of Limerick Generating Station Unit 1 containment isolation logic. On February 22, 2019, while performing work on the 1C Main Seam Line Rad Monitor a partial containment isolation occurred due to a blown fuse. The blown fuse caused a single channel 'C' isolation signal for the Refueling Area Ventilation Exhaust High Radiation and the Reactor Enclosure Ventilation Exhaust-High Radiation logic. The following systems had components that actuated due to the partial isolation: - Plant Process Radiation Monitoring System - Nuclear Boiler System - Control Rod Drive Hydraulic System - Containment Atmospheric Control System - Primary Containment Instrument Gas System This event resulted in partial Group VIC and partial Group VIIIB isolations. All the components that would actuate on a single 'C' isolation signal responded as designed. The licensee notified the NRC Resident Inspector.
ENS 5355622 August 2018 02:00:00LimerickNRC Region 1At 2322 EDT, Limerick Generating Station notified the Pennsylvania DEP (Department of Environmental Protection) that our plant waste water pond (holding pond) overflowed due to heavy rainfall in the area. Plant alignment changes were made and the holding pond stopped overflowing at 0017 EDT. Limerick Generating Station has not determined this release to contain oil, grease, or pollutants hazardous to the public. The licensee notified the NRC Resident Inspector.
ENS 5334117 April 2018 16:29:00LimerickNRC Region 1GE-4Unit 1 HPCI (High Pressure Coolant Injection) was declared inoperable due to a Main Pump seal leak that was identified during surveillance testing. Unit 1 HPCI was declared inoperable at 1030 EDT. HPCI was secured and was manually re-aligned to an available status. At the time of this notification, repairs have been completed and the licensee is making preparations to re-perform the surveillance. The licensee has notified the NRC Resident Inspector.
ENS 531088 December 2017 17:25:00LimerickNRC Region 1GE-4U/2 HPCI (Unit 2/High Pressure Coolant Injection) was declared inoperable due to leak by of the pump discharge check valve after pump shutdown from flow testing. This resulted in cycling of the minimum flow valve. The discharge valve was closed to prevent the continued cycling of the minimum flow valve. This condition was identified during normal surveillance testing. The licensee notified the NRC Resident Inspector.
ENS 5287427 July 2017 18:54:00LimerickNRC Region 1GE-4(Unit 2) HPCI was declared inoperable due to improper valve alignment stemming from an incorrect sequence directed from a work order. (Unit 2) HPCI was inoperable for 20 minutes and was manually re-aligned to an operable status. The licensee notified the NRC Resident Inspector.
ENS 5287124 July 2017 23:50:00LimerickNRC Region 1GE-4At time (2044 EDT), Limerick Generating Station notified the Pennsylvania DEP ( The licensee notified the NRC Resident Inspector.
ENS 527388 May 2017 13:55:00LimerickNRC Region 1GE-4On May 8th, 2017 at 0925 (EDT), during the performance of LGS (Limerick Generating Station) leakage testing of the reactor pressure vessel and associated piping, a through-wall leak was identified on an instrument line connected to the N16D nozzle. The reactor will be maintained shutdown until pipe repairs and testing are complete. The licensee informed the NRC Resident Inspector.
ENS 5245521 December 2016 19:45:00LimerickNRC Region 1GE-4During review of the Limerick future modification list, a concern was raised with a proposed modification for HV-011-015A, ESW (Emergency Service Water) 'A' Discharge to 'B' RHR Service Water Return, which failed to fully close during routine testing. As a result of the failure to close, a clearance was applied and a 10CFR50.59 screening was performed to close and de-energize HV-011-015A and open and de-energize valve HV-011-011A, ESW 'A' Discharge to 'A' RHR (Residual Heat Removal) Service Water Return. This clearance isolated one of the two ESW return flow paths so that only one flow path is available to return cooling water flow to the spray pond. The 10CFR50.59 screening did not address that fire areas 12 (Unit 1 4kV D13 switch gear room) and 18 (Unit 2 4kV D23 switch gear room) are not in compliance with the existing fire safe shutdown (FSSD) analysis. The FSSD analysis credits both flow paths so that Emergency Service Water can be returned to the spray pond. With only one of the two return flow paths available, a single spurious fire induced valve operation can result in deadheading an ESW pump and starving an operating emergency diesel generator of cooling water. Running the emergency diesel generator with a loss of cooling water will initiate a diesel protective trip on high temperature. Compensatory measures are in place for the specific fire areas listed above. The licensee has notified the NRC Resident Inspector.
ENS 5227030 September 2016 02:11:00LimerickNRC Region 1GE-4On 9/29/2016 at 1700 (EDT) the MCR (Main Control Room) was notified of a potential Technical Support Center (TSC) emergency ventilation indication issue following surveillance testing. At 2350 troubleshooting revealed a blown control power fuse which affected functionality of TSC HVAC emergency mode. The system was restored to operable as of 0043 on 9/30/16. If an emergency had been declared and TSC activation was required, the TSC would have been staffed and activated unless the TSC became uninhabitable due to ambient temperatures, radiological or other conditions. The Station Emergency Director would assess habitability in accordance with station procedures. If TSC relocation becomes necessary, then personnel would be directed as required until such time that the TSC emergency ventilation system was returned to service. The licensee informed the NRC Resident Inspector.
ENS 5210118 July 2016 22:43:00LimerickNRC Region 1GE-4Testing of the Everbridge ERO (Emergency Response Organization) notification system identified the system was not able to notify all ERO individuals. This constitutes a loss of offsite communications capability. The issue was subsequently reported resolved by the vendor and site testing has verified resolution at 2037. The Everbridge system capability loss for Limerick was identified at approximately 1600 EDT on July 18, 2016, due to a loss of system communications. Emergency Response Data System (ERDS) capability was not lost. This event is reportable under 10 CFR 50.72(b)(3)(xiii) as a loss of communications capability. The NRC Resident inspector has been notified.
ENS 519681 June 2016 10:40:00LimerickNRC Region 1GE-4Limerick Unit 2 was manually scrammed from 100 (percent) power at 0900 (EDT) on 6/1/2016 in accordance with plant procedure OT-112 'Unexpected/Unexplained change in core flow' when both 2A and 2B Recirculation Pump Adjustable Speed Drives (ASDs) tripped due to an electrical fault. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the Main Steam Bypass valves to the Main Condenser and normal level control using Feedwater. The Manual RPS actuation is reportable under 10 CFR 50.72 (b)(2). All rods inserted fully on manual scram and the plant is in a normal shutdown electrical line up. Unit 1 was not affected by this event. The licensee plans to issue a press release. The licensee notified local counties and Pennsylvania Emergency Management Agency (PEMA). The NRC Resident Inspector has been notified.
ENS 5195224 May 2016 10:12:00LimerickNRC Region 1GE-4On Monday, March 28, 2016, Unit 1 was in OPCON 5 (Refueling) conducting a refueling outage. A modification was being installed for an NSSSS (Nuclear Steam Supply Shutoff System) Test Box on Division 1A Group 1 NSSSS logic. At 0150 hours, a logic jumper was removed as directed by the work order and a logic fuse failed. The fuse failure caused an unplanned invalid actuation of the inboard isolation logic. The isolations were reset and the valves were restored to initial conditions at 0246 hours. On Sunday, April 3, 2016, at 0134 hours, one additional logic fuse opening event occurred during the testing which also caused an invalid actuation which was reset at 0405 hours. The fuse openings occurred during jumper manipulations as the modification was tested on the Division 1A and 1D logic during the refuel outage. The investigation determined the fuse openings were due to the testing process. The suspected devices that caused the condition are not permanent plant equipment and there is no degradation of the actual circuit. They were part of a temporary configuration that was installed to support modification installation and acceptance testing. The temporary devices have been removed. The portion of the primary containment isolation system that received an actuation signal functioned successfully. All of the affected open isolation valves automatically closed. The isolation was a partial actuation. This 60-day ENS report is being made per 10CFR 50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1) to report invalid automatic actuations of systems listed in paragraph (a)(2)(iv)(B). The listed system that actuated was general containment isolation signals affecting containment isolation valves in more than one system. Primary containment isolation valves (PCIVs) closed on reactor water cleanup (RWCU), drywell chilled water (DWCW), primary containment instrument gas (PCIG), drywell sumps and the suppression pool cleanup systems. The licensee has notified the NRC Resident Inspector.
ENS 518474 April 2016 16:49:00LimerickNRC Region 1GE-4Notified the Pennsylvania Department of Environmental Protection that Limerick Cooling Tower water was released to a non-permitted outfall through the spray pond (Ultimate Heat Sink) due to system lineups associated with emergent maintenance activities. There was no radioactive material contained within the water released. Corrective actions are being taken to prevent further release via this outfall. The NRC Resident Inspector will be notified.
ENS 5180920 March 2016 23:51:00LimerickNRC Region 1GE-4During a planned Unit 1 shutdown for a refueling outage, a 0.5 gpm 'pressure boundary leak' was identified on a 1 inch pipe connected to the '1A' RHR-Shutdown Cooling return line by the drywell leak inspection team during a drywell inspection at approximately 15% power. The leak exceeded the TS 3.4.3.2 'Operational Leakage' LCO of no pressure boundary leakage. TS action 'a' was entered which requires to be in at least Hot Shutdown within 12 hours and Cold Shutdown within the next 24 hours. Therefore, the event is reportable within 4 hours per 10CFR50.72(b)(2)(i) due to the initiation of a plant shutdown required by the plant's TS. The event is also reportable within 8 hours per 10CFR50.72(b)(3)(ii) due to an event that resulted in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded. TS 1.28 defines Pressure Boundary Leakage as leakage through a nonisolable fault in a reactor coolant system component body, pipe wall or vessel wall; therefore, the leak is a 'pressure boundary leak' as defined in TS. The licensee notified the NRC resident Inspector.
ENS 517737 March 2016 11:29:00LimerickNRC Region 1GE-4At the Limerick Generating Station, an individual experiencing a non-occupational illness was taken to a local medical facility. The individual was not contaminated. Subsequently, Limerick was informed that the individual has suffered a fatality. The individual was a contract employee and was located in a clean break area, within the protected area, when the individual became ill. The licensee has notified the NRC Resident Inspector and OSHA.
ENS 5174922 February 2016 16:19:00LimerickNRC Region 1GE-4Limerick Generating Station Main Control Room was informed that a Limerick Emergency Preparedness Zone (EPZ) siren located in Skippack Township, Montgomery County, Pennsylvania was sounding by an off-site vendor. This notification is being made in accordance with SAF 1.9 due to a spurious actuation of Limerick Emergency Preparedness Zone (EPZ) siren. The alarm actuated for approximately 90 seconds following preventative maintenance. No actual plant emergency exists. All Limerick EPZ sirens remain functional; no other reportability threshold(s) have been met or exceeded. The licensee informed State and local authorities and the NRC Resident Inspector.
ENS 5161419 December 2015 10:38:00LimerickNRC Region 1GE-4At 0702 EST on 12/19/2015, the Unit 2 reactor automatically scrammed on a valid reactor low level signal (12.5 inches). The reactor low level signal was caused by the trip of the in-service 2A Reactor Feedwater Pump, causing reactor level to lower, exceeding the low reactor level setpoint of 12.5 inches. The shutdown was normal. The plant is stable in Hot Shutdown with normal reactor level, pressure control via the Main Steam Bypass Valves to the Main Condenser and normal level control using the Condensate System. High level trip of the 2A Reactor Feedwater Pump was caused by high reactor level of +54 inches following opening of bypass valves during reactor start-up and pressurization. The cause is still being investigated. All systems functioned as expected following the reactor scram. The licensee notified the NRC Resident Inspector.
ENS 513683 September 2015 22:04:00LimerickNRC Region 1GE-4At 1901 EDT on 9/3/2015, the Unit 2 HPCI system inboard steam supply valve isolated due to a high steam flow instrument failure. The inboard steam supply valve closed and isolated as expected. There were no indications of a steam leak. Drywell parameters and affected Reactor Enclosure rooms and piping areas were inspected with no indications of a steam leak. In addition, the steam leak detection system did not indicate any rising temperatures for any of the affected areas. The issue has caused Unit 2 HPCI to be declared inoperable and unavailable. Unit 2 has entered into a 14 day (Technical Specification) Limited Condition of Operation per T.S. 3.5.1. The licensee notified the NRC Resident Inspector.
ENS 5116821 June 2015 20:25:00LimerickNRC Region 1GE-4In response to a trip of Unit 2 reactor enclosure HVAC (Heating, Ventilation and Air Conditioning), subsequent loss of reactor enclosure delta-p and rising reactor enclosure room temperatures, a Unit 2 manual secondary containment isolation was initiated per station procedures. This manual isolation also resulted in an isolation signal to containment atmosphere control (CAC) system valves and primary containment instrument gas (PCIG) system valves. System responses were as expected. Unit 2 secondary containment delta-p and room temperatures were restored via the standby gas treatment system (SGTS), and Unit 2 secondary containment integrity remains intact and operable. Investigation of the trip of Unit 2 reactor enclosure HVAC is ongoing. This is being reported under 50.72(b)(3)(iv)(A) for containment isolation signal affecting containment isolation valves in more than one system. The licensee informed the NRC Resident Inspector.
ENS 5098113 April 2015 09:56:00LimerickNRC Region 1GE-4Following a pre-planned scram for entry into the U2 Refueling Outage, the 'B' Reactor Protection system (RPS) was unable to be reset due to a deficiency with the '2H' Intermediate Range Power Monitor. Due to this failure to reset RPS, a manual full scram was initiated as required by plant procedures. The licensee notified the NRC Resident Inspector.
ENS 509565 April 2015 16:06:00LimerickNRC Region 1GE-4

An Alert was declared due to a fire in a Unit 2 Division 2 Safeguard (250 volt) DC Motor Control Center. This has made the High Pressure Core Injection system inoperable and unavailable. The fire is out. The emergency response organization has been activated and investigation / repair planning will commence. Unit 2 is stable with no other system affects. The fire was extinguished by on-site personnel. No off-site responders were required. The Reactor Core Isolation Cooling system remains operable. A Fire Watch has been stationed to monitor for fire reflash. There were no injuries resulting from this event. There was no effect on Unit 1. The licensee notified the NRC Resident Inspector and State and local government agencies. Notified the following organizations: DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, FDA EOC, FEMA NWC, and Nuclear SSA.

  • * * UPDATE FROM DAN BOYLAN TO DONALD NORWOOD AT 1812 EDT ON 04/05/15 * * *

The Alert was terminated at 1742 EDT. The licensee notified the NRC Resident Inspector and State and local government agencies. Notified R1DO (Kennedy), IRD (Gott), and NRR EO (Morris). Notified the following organizations: DHS SWO, DOE Ops Center, FEMA Ops Center, HHS Ops Center, NICC Watch Officer, USDA Ops Center, EPA EOC, FDA EOC, FEMA NWC, and Nuclear SSA.

ENS 509513 April 2015 11:54:00LimerickNRC Region 1GE-4Limerick Generating Station (LGS) has completed a review of recent seismic monitor performance. The seismic monitor is currently capable of fulfilling its emergency assessment support function. The review of the system performance over the last three years identified two occasions when the system was degraded and incapable of performing its emergency assessment support function such that emergency classification at the UNUSUAL EVENT and ALERT levels could not be declared within fifteen minutes as required with site instrumentation. The seismic monitor was determined to be degraded and incapable of performing its emergency assessment support function on the following dates: 1) January 17, 2014 - Unit 1 100% power, Unit 2 97% power 2) March 22, 2014 - Unit 1 Refueling, Unit 2 100% power These unplanned inoperable conditions of the seismic monitor were entered into the LGS Corrective Action Program (CAP) when they occurred. While Exelon procedural direction allowed the use of offsite sources to obtain seismic data when the seismic monitor is incapable of assessing emergency plan Emergency Action Levels (EALs), this was not explicitly referenced in the approved EALs. The loss of assessment capability is reportable to the NRC within 8 hours of discovery in accordance with 10 CFR 50.72(b)(3)(xiii). This report is required per 10 CFR 50.72(a)(1)(ii) as an event that occurred within 3 years of the date of discovery. For the two dates above, the 1/17/14 failure was related to function of the system CPU (central processing unit) and the 3/22/14 failure was due to a failed instrument backup battery. There was no seismic event on either of these two dates. The licensee informed the NRC Resident Inspector.
ENS 5084724 February 2015 01:02:00LimerickNRC Region 1GE-4At 2140 EST on 02/23/2015, Unit 1 reactor automatically scrammed on a valid reactor high pressure signal (1096#). The reactor high pressure signal was caused by the closure of the 1C inboard main steam isolation valve (MSIV), causing reactor pressure to rise, exceeding the reactor protection system (RPS) setpoint of 1096# pressure. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the main steam bypass valves to the main condenser and normal level control using the feedwater system. The closure of the 1C inboard MSIV appears to have been caused by a loss of primary containment instrument gas (PCIG) pneumatic supply to the valve. Instrument air was aligned to the remaining MSIV's. Limerick Unit 1 will remain in Hot Shutdown until repairs can be made. All rods inserted into the core during the scram. No relief or safety valves actuated during the transient. The electric grid is stable and supplying all plant loads. There was no affect on Unit 2. The licensee notified the NRC Resident Inspector, Pennsylvania Emergency Management Agency, and Berks, Chester and Montgomery counties.
ENS 5067011 December 2014 14:52:00LimerickNRC Region 1GE-4Station personnel simultaneously opened the inner and outer air lock doors from Unit 2 Reactor Enclosure to the Refuel Floor. Reactor Enclosure Secondary Containment Integrity was declared inoperable per Unit 2 TS 3.6.5.1.1, due to failure to meet surveillance requirement U2 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on 352' momentarily open at the same time. Reactor Enclosure D/P (differential pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared operable following verification that at least one air lock door to each access of secondary containment was closed per U2 TS 4.6.5.1.1.b.2. Total time was approximately 5 seconds. The secondary containment doors do not have a mechanical interlock and this event has been classified as a human performance error. The licensee notified the NRC Resident Inspector
ENS 505188 October 2014 07:24:00LimerickNRC Region 1GE-4This notification is being made as a result of notifications to other government agencies. A sodium hypochlorite leak occurred on site at Limerick Generating station on 10/7/14, that had the potential to enter the environment. The leak has been isolated. A flow control valve in the U1 cooling tower chemical treatment system caused the leak. The sodium hypochlorite that leaked was deposited into the onsite Holding Pond. The Holding Pond was being discharged at the time of the leak in accordance with procedures to support normal plant operations. The leak was discovered at 2110 hours (EDT on 10/7/14) and isolated at 2115 hours. The Holding Pond discharge was secured at 2125 hours. Sampling of the Holding Pond confirmed the presence of sodium hypochlorite. Since the Holding Pond was being released at the time of the leak, there is a potential that greater than 67 gallons of sodium hypochlorite could have been released to the Schuylkill River. This report is being made due to the potential that a reportable quantity of sodium hypochlorite could have discharged to the Schuylkill River while the Holding Pond was releasing during the sodium hypochlorite leak. Evaluations are being performed to quantify this actual volume of sodium hypochlorite that was discharged as a result of the leak. The licensee has notified the NRC Resident Inspector and state and local authorities.
ENS 5037617 August 2014 11:21:00LimerickNRC Region 1GE-4On 8/17/2014 at 0400 EDT, the Technical Support Center (TSC) emergency ventilation system was identified as inoperable. Troubleshooting of this equipment found a blown control power fuse. The system has been restored to operational status as of 0555 EDT on 8/17/2014. If an emergency had been declared and TSC activation was required, the TSC would have been staffed and activated unless the TSC became uninhabitable due to ambient temperatures, radiological or other conditions. The station Emergency Director would assess habitability in accordance with station procedures. TSC relocation of personnel would be directed as required until such time that the TSC emergency ventilation system was returned to service. The licensee notified the NRC Resident Inspector.
ENS 500078 April 2014 09:45:00LimerickNRC Region 1GE-4U1 entered Technical Specification 3.0.3, and initiated actions to reduce power via control rod insertion in preparations to enter startup within the following 6 hours. Entry into Tech Spec 3.0.3 was a result of both HPCI and RCIC injection systems being inoperable at the same time. During startup from the U1 refueling outage, RCIC and HPCI full flow testing was unable to be completed at rated reactor pressure prior to the expiration of the 12 hour allowance per Tech Spec Surveillances 4.7.3.b* and 4.5.1.b.3** respectively. This occurred due to testing issues encountered while attempting to perform the rated pressure pump valve and flow tests. U1 HPCI testing was completed satisfactorily at 0830, and HPCI was restored to operable. Plant shutdown was terminated at 0830 (EDT) as conditions for 3.0.3 no longer existed. The licensee will notify the NRC Resident Inspector.
ENS 498715 March 2014 02:26:00LimerickNRC Region 1GE-4At 2334 EST on 3/4/14 Unit 1 was manually scammed during a Rapid Plant Shutdown. The Rapid Plant Shutdown was initiated due to an Electro Hydraulic (Control) (EHC) System failure resulting in all Low Pressure Turbine lntercept Valves failing closed. The shutdown was normal and the plant is stable in Hot Shutdown with normal pressure control via the Main Steam Bypass Valves to the Main Condenser and normal level control using Feedwater. The licensee informed both State and local agencies and the NRC Resident Inspector. A press release will be issued by the licensee.
ENS 4984219 February 2014 15:32:00LimerickNRC Region 1GE-4On 2/19/2014 at 1019 EST, the Technical Support Center emergency ventilation system failed to operate during TSC Ventilation Operability Check per EP-MA-124-1001-F-02 performed by Limerick Emergency Preparedness staff. Troubleshooting of this equipment deficiency found a blown control power fuse. The fuse failure is attributed to its age. The system has been restored to operational status as of 1430 EST on 2/19/2014. If an emergency had been declared and TSC activation was required, the TSC would have been staffed and activated unless the TSC became uninhabitable due to ambient temperatures, radiological or other conditions. The Station Emergency Director would assess habitability in accordance with station procedures. TSC relocation of personnel would be directed as required until such time that the TSC emergency ventilation system was returned to service. The licensee notified the NRC Resident Inspector.
ENS 497069 January 2014 15:21:00LimerickNRC Region 1GE-4Station Personnel simultaneously opened the inner and outer air lock doors from Unit 2 (U2) Reactor Enclosure to the Refuel Floor. Reactor Enclosure Secondary Containment Integrity was declared Inoperable per U2 TS 3.6.5.1.1, due to failure to meet surveillance requirement U2 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on 352' momentarily open at the same time. Reactor Enclosure D/P(differential pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared Operable following verification that at least one air lock door to each access of secondary containment was closed per U2 TS 4.6.5.1.1.b.2. Total (Limiting Condition for Operation) time was approximately 5 seconds. The NRC Resident Inspector has been informed.
ENS 496914 January 2014 01:22:00LimerickNRC Region 1GE-4Limerick Generating Station Main Control Room was informed that a Limerick Emergency Preparedness Zone (EPZ) Siren located in South Coventry, Chester County Pennsylvania area was sounding by an off-duty plant employee and confirmed by the Chester County 911 Dispatch Center. Notification occurred at 2300 hours on 1/13/14. This notification is being made in accordance with SAF 1.9 due to a spurious actuation of Limerick Emergency Preparedness Zone (EPZ) Siren. The siren maintenance contractor has been contacted to investigate and silence the sounding alarm. No actual Plant emergency exists. The siren activation was caused by equipment malfunction. (The) remaining 164 of 165 Limerick EPZ Sirens remain functional, no other reportability threshold(s) have been met or exceeded. The licensee has notified the NRC Resident Inspector and state and local authorities.
ENS 4965918 December 2013 18:50:00LimerickNRC Region 1GE-4Station Personnel simultaneously opened the inner and outer air lock doors from Unit 2 Reactor Enclosure to the Refuel Floor. Reactor Enclosure Secondary Containment Integrity was declared inoperable per U2 TS 3.6.5.1.1, due to failure to meet surveillance requirement U2 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on the 352 foot elevation being momentarily open at the same time. Reactor Enclosure D/P (differential pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared Operable following verification that at least one air lock door to each access of secondary containment was closed per U2 TS 4.6.5.1.1.b.2. Total LCO time was approximately 5 seconds. The licensee notified the NRC Resident Inspector.
ENS 4965118 December 2013 12:22:00LimerickNRC Region 1GE-4Station Personnel simultaneously opened the inner and outer air lock doors from Unit 1 Reactor Enclosure to the Radwaste Enclosure. Reactor Enclosure Secondary Containment Integrity was declared inoperable per U1 TS 3.6.5.1.1, due to failure to meet surveillance requirement U1 TS 4.6.5.1.1.b.2, due to the report of both containment airlock doors on 217 (foot elevation, being) momentarily open at the same time. Reactor Enclosure D/P (delta pressure) remained steady at 0.35 inches vacuum water gauge. Reactor Enclosure Secondary Containment Integrity was declared Operable following verification that at least one air lock door to each access of secondary containment was closed per U1 TS 4.6.5.1.1.b.2. Total LCO time was approximately 5 seconds. The licensee has notified the NRC Resident Inspector.
ENS 4964417 December 2013 15:11:00LimerickNRC Region 1GE-4A licensed operator had a confirmed positive for alcohol during a random fitness for duty test. The employee's access to the plant has been restricted. The licensee has notified the NRC Resident Inspector.
ENS 4952610 November 2013 16:16:00LimerickNRC Region 1GE-4Station personnel simultaneously opened the inner and outer air lock doors from the unit 1 reactor enclosure to the radwaste enclosure. Reactor enclosure secondary containment integrity was declared INOPERABLE per TS 4.6.5.1.1.b.2 due to report of both containment airlock doors on the 217 foot elevation being momentarily open at the same time. Reactor enclosure D/P (differential pressure) remained steady at .35 inches water column. Reactor enclosure secondary containment integrity was declared OPERABLE following verification that at least one airlock door to each access of secondary containment was closed per U1 TS 4.6.5.1.1.b.2. Total LCO time was approximately 10 seconds. The licensee has notified the NRC Resident Inspector.
ENS 493183 September 2013 14:10:00LimerickNRC Region 1GE-4During planned maintenance activities, station personnel simultaneously opened the inner and outer airlock doors from unit 2 reactor enclosure to the U2 reactor enclosure HVAC room, resulting in a lowering of reactor enclosure delta pressure to below the tech spec minimum required value. The airlock doors were closed within approximately 5 seconds and reactor enclosure delta pressure recovered to greater than the tech spec minimum required value within approximately 20 seconds. Unit 2 secondary containment was declared inoperable for the time that reactor enclosure delta pressure was below the tech spec minimum required value, and was declared operable when reactor enclosure delta pressure recovered to greater than the tech spec minimum required value. Total Limiting Condition of Operation time was approximately 20 seconds. The licensee has notified the NRC Resident Inspector.
ENS 4927513 August 2013 14:46:00LimerickNRC Region 1GE-4

This ENS (event notification) is being issued in advance of planned corrective maintenance on a TSC (Technical Support Center) HVAC (Heating Ventilation Air Conditioning) power supply. On 8/13/2013 at 1600 (EDT), the Technical Support Center ventilation system will be removed from service to perform corrective maintenance on an electrical panel that supplies power to the system. The emergency ventilation system will not be available and cannot be restored within the time period required to staff and activate the Emergency Response Organization (ERO). The work is scheduled to complete on 8/13/2013 at 1800 (EDT). If an emergency is declared and the TSC activation is required, the TSC will be staffed and activated unless the TSC becomes uninhabitable due to ambient temperatures, radiological or other conditions. The Station Emergency Director would assess habitability in accordance with station procedures. TSC relocation of personnel would be directed as required until such time that the TSC ventilation system is returned to service. An update will be sent upon TSC HVAC restoration. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM MARK ARNOSKY TO JOHN SHOEMAKER AT 2255 EDT ON 8/13/13 * * *

At 2030 EDT on 8/13/13, the TSC emergency ventilation system has been restored to normal. The licensee notified the NRC Resident Inspector. Notified R1DO (Powell).

ENS 492395 August 2013 21:38:00LimerickNRC Region 1GE-4Both Limerick 4 KV offsite sources were inoperable and Technical Specification 3.0.3 was entered for Unit 2 from 1456 to 1512 (EDT) during D23 4KV Undervoltage testing. During the undervoltage test, the affected diesel and one offsite source (101 Bus) are inoperable. During the test, the alternate offsite source (201 Bus) UV relay was tested and found to be inoperable, resulting in the need to declare the second offsite source (201 Bus) inoperable. When notified of the failure, action was taken to restore the 101 Bus offsite source to operable and exit the 3.0.3 condition (at) (1512 EDT). The 201 Bus Relay was successfully calibrated and tested to subsequently restore the 201 Bus to operability (at) (1543 EDT). Testing of the 201 bus UV relay is directed per procedure while the 101 bus is powered from the diesel generator. The licensee notified the NRC Resident Inspector.
ENS 4902410 May 2013 18:08:00LimerickNRC Region 1GE-4A Non-licensed, Supervisory employee had a confirmed positive alcohol test during a random fitness-for-duty test. The employee's access to the Plant has been removed. The licensee informed the NRC Resident Inspector.
ENS 4896324 April 2013 16:50:00LimerickNRC Region 1GE-4A non-licensed, supervisory employee had a confirmed positive for alcohol during a random fitness-for-duty test. The employee's access to the plant has been restricted. The licensee has notified the NRC Resident Inspector.
ENS 4893617 April 2013 02:11:00LimerickNRC Region 1GE-4During outage main turbine stop valve RPS logic surveillance testing, an invalid RPS actuation occurred due to an error in executing main turbine surveillance testing procedures. A Turbine Stop Valve closure RPS signal occurred due to an error in the restoration sequence of restoring the RPS bypass signal and a subsequent manual trip of the main turbine. This resulted in a full scram and a trip of both reactor recirculation pumps. The site post-scram response procedure was entered, which required that the mode switch be placed in the locked SHUTDOWN position. This caused an expected but valid RPS actuation. No control rod motion occurred due to all control rods were inserted at the time of the invalid RPS actuation and subsequent valid RPS actuation. The license has notified the NRC Resident Inspector.
ENS 4883720 March 2013 20:52:00LimerickNRC Region 1GE-4

After securing the Unit 1 HPCI turbine from service following a planned pump, valve, and flow surveillance test an oil leak of approximately 1 pint per minute developed. The oil leak was stopped by securing the auxiliary oil pump for the HPCI system. There was no loss of oil pressure while the HPCI turbine was operating. This issue has caused the Unit 1 HPCI system to be declared inoperable and unavailable. Per LGS (Limerick Generating Station) Unit 1 Technical Specifications section 3.5.1, the HPCI system must be restored to operable status within 14 days. The cause of the oil leak is being investigated." The licensee notified the NRC Resident Inspector.

  • * * UPDATE FROM DANIEL WILLIAMSON TO DONALD NORWOOD AT 1510 EDT ON MARCH 21, 2013 * * *

UNIT 1 HPCI has been restored to operable status following repairs and post-maintenance testing at 1300 EDT on March 21, 2013. The licensee changed the reporting requirement from 10CFR50.72(b)(3)(ii)(A) to 10CFR50.72(b)(3)(v((D). The licensee will notify the NRC Resident Inspector. Notified R1DO (Trapp).

ENS 4882415 March 2013 17:23:00LimerickNRC Region 1GE-4This Part 21 initial notification addresses a pump impeller defect that resulted in a post maintenance test (PMT) failure. The 0C RHR Service Water Pump was being replaced due to degraded performance which caused an In-Service Test (IST) failure. The replacement pump impeller received from the supplier had not been machined to the purchase order specifications. The IST of the new pump could not be completed since the required test conditions could not be established. The pump was later replaced and the IST was completed successfully. The pump was declared operable on March 2, 2013. This Part 21 Initial Notification is being submitted pursuant to the requirements of 10CFR21.21 (d)(3)(i). The licensee has notified the NRC Resident Inspector.
ENS 486536 January 2013 13:32:00LimerickNRC Region 1GE-4

This ENS (report) is being issued in advance of planned corrective maintenance on a TSC HVAC power supply. On 1/6/13 at 2000 (EST), the Technical Support Center Emergency Ventilation system will be removed from service to perform corrective maintenance on the load center that supplies power to the TSC HVAC system. The emergency ventilation system will not be available and cannot be restored within the time period required to staff and activate the Emergency Response Organization (ERO). The work is scheduled to complete on Friday 1/11/13 at 1500 (EST). If an emergency is declared and the TSC activation is required, the TSC will be staffed and activated unless the TSC becomes uninhabitable due to ambient temperatures, radiological or other conditions. The Station Emergency Director would assess habitability in accordance with station procedures. TSC relocation of personnel would be directed as required until such time that the TSC ventilation system is returned to service. An update will be sent upon TSC HVAC restoration. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE FROM WILLIAMSON TO KLCO ON 1/10/13 AT 2209 EST* * *

The TSC emergency ventilation system was restored to normal at 2200 EST on 1/10/13. The licensee notified the NRC Resident Inspector. Notified the R1DO (Newport).

ENS 4862928 December 2012 09:55:00LimerickNRC Region 1GE-4

Limerick and associated local counties have lost communications with all Emergency Planning Zones (EPZ) sirens for greater than 1 hour. This exceeds the 25% notification threshold. The contract vendor is responding to the loss to determine repair actions and timeline. The EPZ plan contains alternate methods of notifying the public in the event of an evacuation. Notifications have been made to the State and local agencies regarding this loss of Emergency Preparedness capability at 0913 EST on 12/28/12, which constitutes the 'Offsite Notification' per 10CFR50.72(b)(2)(xi). The licensee has notified Montgomery, Chester, Burkes counties, and the NRC Resident Inspector.

  • * * UPDATE AT 1258 EST ON 12/28/12 FROM DAN WILLIAMSON TO HUFFMAN * * *

Communications with all EPZ sirens have been restored. The licensee will notify the affected counties and the NRC Resident Inspector. R1DO (Conte) notified.

ENS 4857510 December 2012 21:40:00LimerickNRC Region 1GE-4On Saturday, October 13, 2012, Unit 1 was operating at 100% power. At 1841 (EDT), the 1A RPS/UPS inverter tripped and the automatic transfer of the RPS and UPS 120 VAC distribution panel (1A-Y160) loads to the primary alternate AC power source was delayed. The delay in automatic load transfer caused the RPS series breakers to trip on undervoltage. The failure caused a loss of power to Division IA and IIA RPS relays and Division IA and IIA NS4 relays. This caused primary containment isolation valves (PClVs) to automatically close on more than one system. The IB and IIB channels were unaffected. The most probable cause for the delayed load transfer was a failed logic power supply with a momentary loss of synchronization. Troubleshooting continues (in order) to confirm the specific cause of the component failure. The distribution panel loads are currently supplied by an installed alternate AC power source. The portion of the primary containment isolation system that received an actuation signal functioned successfully. All of the affected open isolation valves automatically closed. The isolation was a partial actuation. This 60-day ENS report is being made per 10CFR50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1) to report invalid automatic actuations of systems listed in paragraph (a)(2)(iv)(B). The listed system that actuated was general containment isolation signals affecting containment isolation valves in more than one system. Primary containment isolation valves (PCIVs) closed on drywell chilled water (DWCW), reactor enclosure cooling water (RECW), primary containment instrument gas (PCIG), Unit 1 containment leak detector, and Unit 2 containment leak detector. The licensee notified the NRC Resident Inspector.
ENS 483723 October 2012 20:22:00LimerickNRC Region 1GE-4During logic and cable routing reviews for Multiple Spurious Operations (MSO), an existing unprotected cable issue was identified that impacts the D22 emergency Diesel Generator (EDG) output breaker. This unprotected cable could fail due to fire damage in fire area 067W when the associated 4kV safeguard bus is credited for Post-Fire Safe Shutdown. The single spurious fire induced cable failure identified can cause the D22 EDG output breaker to spuriously close when the 4kV safeguard bus is credited using the offsite power source. The existing fire safe shutdown analysis failed to identify this cable required protection in order to credit the 4kV safeguard bus in area 067W postulated fire. The licensee has notified the NRC Resident Inspector.